Stable mercury isotopes stored in Masson Pinus tree rings as atmospheric mercury archives

Amsterdam

2021

9 S.

Sonderdruck

12802S

40002234

The accuracy of mercury (Hg) dendrochemistry has been questioned because significant knowledge gaps exist in understanding the Hg translocation and mobility in tree-ring. In this study, we evaluated Hg concentrations and isotopic profiles in the tree-ring at a Hg artisanal mining site and a control site with the documented local Hg production inventory. Results show that the Hg concentration accumulated in tree-ring fails to reconstruct the temporal trend of Hg production due to confounded tree physiological and environmental factors, specifically, the radial translocation and tree age effects occurring during the fast-growing period. The temporal profiles of δ202Hg exhibit pronounced tree-specific variabilities due to the complexity of Hg isotopic mass dependent fractionation during atmospheric Hg uptake and translocation in vegetation. The Hg odd-MIF (mass independent fractionation) profiles in tree-ring can reconstruct a decadal-scale temporal trend of the atmospheric Hg0 pollution level, and also be used as a tracer to distinguish the emission source shifts of atmospheric Hg0. However, the radial translocation would result in uncertainties at the higher resolution because of the mixing of odd-MIF signatures with active rings. Caution should be taken and additional supporting evidence collected from independent methods should be used for verifying the tree-ring records.Keywords: Mercury isotopes; Tree rings; Radial translocation; Mercury pollution